In manufacturing a semiconductor device, a process for forming a wiring such as, for example, an interconnection line or a contact, is performed. As for this process, a process called damascene process is used. In the damascene process, a shape such as a groove or a hole is formed in an interlayer insulation film by etching, and a processing of burying a metal material in the formed groove or hole is performed. According to recent miniaturization of a wiring, however, various problems occur in that it becomes difficult to bury a metal material in a fine hole or groove.
In order to cope with the above-described problems in the damascene process, a process has been proposed in which a copper layer is deposited and then the copper layer is etched so as to form a fine copper wiring. Such a process is disclosed in a paper entitled “Low-Temperature Etching of Cu by Hydrogen-Based Plasma”, Fangyu Wu et al., ACS APPLIED MATERIALS & INTERFACES, 2010, Vol. 2, No. 8, p. 2175-2179. In the process disclosed in the paper, when a copper layer is exposed to plasma of a processing gas containing hydrogen gas and argon gas, the copper layer is etched.